Technological Field
The present disclosure relates to a technique for controlling a lockdown of a cache memory.
Description of the Related Art
Processing executed by an image forming apparatus includes mechanical-control processing, and best-effort type processing (hereinafter also referred to as “best-effort processing”). The mechanical-control processing is processing for controlling each device in the image forming apparatus, and processing that requires real-time performance. The best-effort processing does not require the real-time performance to such an extent that the mechanical-control processing requires the real-time performance. However, the best-effort processing requires usability.
Conventionally, an image forming apparatus executes mechanical-control processing and best-effort processing by separate Central Processing Units (CPUs). In contrast to this, in recent years, an image forming apparatus that executes mechanical-control processing and best-effort processing by sharing a CPU is achieving widespread use. In this case, a control program for the mechanical-control processing and a control program for the best-effort processing share a cache memory.
As a technique related to cache memories, JP 2000-250518 A discloses a character processing device “that is capable of processing high-quality character data at high speed without causing the storage capacity to be increased”. By initialization processing, the character processing device saves character codes and frequently used font data in a cache area allocated in a Random Access Memory (RAM), thereby speeding up these data accesses.
When a control program for the mechanical-control processing and a control program for the best-effort processing share a cache memory, there occurs a possibility that the cache memory will be occupied, by one control program. In this case, the image forming apparatus cannot store the other control program in the cache memory, and consequently the processing time of the other control program becomes longer than intended. For the purpose of preventing the above, there is a technique called “cache lockdown”. The cache lockdown is a technique for locking the contents of a cache memory so as to prevent a control program written to the cache memory from being overwritten by the other control program. Conventionally, the image forming apparatus stores a control program for executing a series of processing in a cache memory, and then locks down the whole cache memory.
If the whole cache memory is locked down, the lockdown is not disabled until the execution of the control program to be locked down is completed. Therefore, in a case where a new control program is required to be locked down, the image forming apparatus cannot lock down the new control program. As the result, there is a possibility that the processing time of the new control program will become longer than intended. Therefore, an image forming apparatus that is capable of preventing the execution of a control program having a high priority from delaying is desired.